Apparatus for concentrating ores



E. w. DAVIS APPARATUS FORiCONCENTRATING ORES May 28, 1935.

Filed April 11 1 1 5 shets-sneet 1 [award/2741713- I I I I n l l l l l l l I l I l I ll (Illll y 9 E. w DAVIS I APPARATUS FOR CONCENTRATI NG DRESS 3 Sheets-Shet 2* Filed April 11, 1931 v awm rntoz Edward Wflaw's' $5 111s wh m I May 28', 193.5. I w.-DAv|s APPARATUS FOR CONCENTRATING ORES Filed April 1 1, 1951' 3 Sheets-Sheet s I avwmto p' id1mvd ifflalak' 33 10;? QHZOWMd III I l.

out loss of magnetic mineral Patented May 28, 1935 UNITED -=srAT I 2,00z,97&1 I

PATENT OFFICE ff APPARATUS FOR, CONCENTRATING ORES 7 Edward Wilson Davis, Minneapolis, Minn. 0 Application April 11,1931, Serial No. 529,412

' '15'Claims. (01; 209-232) My invention relates to an improved apparatus for the concentration of iron ore in -which magnetic force or-attraction is utilized to cause the adhering together and precipitation of particles of iron mineral, such as magnetite, which maybe mingled with particles of sand or gravel of substantially equal weight and which in a grayity separator would be carried out with the tailings of themachine. I

This application is a continuation in part of my application SerialNo. 431,092, filed February 25, 1930,. and the invention is an improvement on the apparatus described in my UnitedStates Patent No. 1,153,037 issued September-5, 1915.

The present invention provides means for more accurate control of the concentrating operation with'resultant cleaner-separation of the magnetic mineral particles from the gangue particles and with production of a concentrate containing a relatively small amountof water as compared with the product of earlier practice. My invention further makes it possible to'treat relatively coarsely comminuted ores and effects an increase in the capacity of the apparatus as compared with apparatus of similar size heretoforeused. i

In the earlier apparatus, as described in my Patent No. 1,153,037, it was found that only finely comminute'd ores could besatisfactorily concentrated. I With relatively coarsely comminuted ores, the coarser gangue'parti'c'lescould not be'overflowed at the tailings weir except by increasing the rate of agitation to a point where considerable loss of magnetic mineral particles in the overflow would result. After considerable experimental work and study, it has been discovered that by maintaining a condition of relatively low agitation near the tailings overflow Weir and increasing the density of the pulp the coarser gangue particles can be flowed over with particles.At the same time, it is necessary to maintain a higher degree of agitation in the .upper portions of the inclined troughs in which the pulp is treated in .order to produce sufficient agitation for cleaning the concentrate. I have found that these two functions can be performed simultaneously in the same apparatus by providing spiral agitating and conveying scrapers having a very small pitch at the lower or tailings "overflow end of the ap paratus' and a higher pitch at the. upper end.

Further, by thus varying the pitch of the spiralsto a suitable extent, it is possible torotate the spirals at a higher speed than in apparatus hitherto used and thereby increase the capacity without increasing loss of the magnetic mineral. By

1 ing 'gangue tached'to and locked within the "magnetic ma- 2,5,

embodying my invention. 1

operating with a denser pulp, economy in the use of water is also eifected. 1 v e It-has further been discovered that for the best results, namely, large capacity, high grade con-' centrate and low. tailing losses, it is advan- 5 tageoustoregulate the clearance between thespirals and the strongmagnetic pole pieces of the apparatus. It has been found-that when the clearance issmall, the grade of the concentrate is lower, whereaswhen-the clearance isgreater 0.-

and within certain limits depending upon thefineness and character of theme, the grade of theconcentrate is raised to'a marked degree, without undue decrease in capacity and without increase in tailing losses. This improvementmay' 15 be explained as due to-the fact that with the greater clearanca greater washing action is per mittediand the spirals function not onlyas con veyors for moving the concentrate upwardly of;

the troughs toward the concentrate discharge, 1.

but also to a greater extent'as agitators; to stir and break up the bodies of the magnetic material adhering to the magnets, .therebyfliberat-' particles that may have become atterial.- A'further featureof the invention, therefore, consists of means for adjusting the relation of the spirals to the strong pole pieces so as to regulate the grade of the concentrateas desired and also to compensate for wear of the spirals. I 30,-.

Another feature of sists in so arranging lating the rotation of ing scrapers thereto it is collected and troughs toward the concentrate discharge and the non-magnetic gangue mineral flowing'down toward the tailings overflow tend to follow separate paths and thereby keep from becoming remixed. I

Still another feature of the invention resides inthe'provision'of an elevated discharge for the the present'invention conthe pole' pieces and correthe agitating and conveythat the iron mineral as concentrate whereby the carrying forward'with conveyed up the inclined 351 the scrapers are operated 5:

Figure 2 is a longitudinal sectional elevation.

Figure 3 is a detail view of the agitating and conveying means included in the apparatus shown in Figures 1 and 2.

Figure 4 is a transverse sectional elevation taken on line 4-4 of Figure 2.

Figure 5 is a transverse sectional elevation taken on line 5--5 of Figure 2. 7

Figure 6 is a detail view in plan of the spiral driving means showing bearing adjustments.

Figure 7 is a sectional view taken on line 'I-I of Figure 6.

Figure 8 is a sectional of Figure '7.

Figure 9 is adetail view in end elevationof the spiral driving means showing bearing adjustments.

Figure 10 is a view taken on line 8-8 diagram showing the movement of spiral for adjustment as wear decreases its.

diameter.

In'the drawings, It! represents a concentrator of the log washer type including two inclined troughs l2, semi-circular in cross-section and formed by theenergized pole piece l4, the'nonmagnetic bottom plates IS, the filler pieces. 18 and the side walls 20. Mounted to rotatein the troughs I2 are shafts 22 and 24 carrying continuous spiral agitating and conveying scrapers 26 made of a non-magnetic material such as copdriven through like, The shafts 22 and 24 are suitable gears 21 by any convenient power means'not shown. The pole piece I4 is magnetized bythe magnets 28 having suitable windings 30. The filler pieces I8 are likewise energized but it is important that the windings or other arrangements provided for this purpose are such thatthe magnetic fields established by. such pieces shall be weaker than the piece 14, for the per, brass or the drawings, the filler pieces l8 are arranged in cirgang'ue from cuit with the magnets 28 through the base member 29 and the sidemembers I9. I have shown two troughs in the drawings, but any number may be used. The overflow weir 32 and a launder 34 are provided at the lower end'of the concentrator for discharge of the tailings, and at the upper end is a chute having an inlet opening 36 elevated above the bottom of the troughs to prevent water introduced for washing the concentrate in the upper portion of the troughs from flowing out with the concentrate insteadof passing downwardly through the lower ends of'the troughs. In the drawings, the pole piece I4 is shown as terminating just short of the opening 36 and a raised lip 40 of suitable sheet metal is provided for effecting the elevated discharge.

The .ore to be treated is fed'by. any suitable means into the feed box 42 at a point near the lower end of the apparatus from which it passes into the troughs l2 through the opening 44. Water pipes, not shown, are provided near the feed inlet to keep Spray pipes 46 are so placed as to wash the the material on the curved filler pieces 18 andthe pole piece l4 onto the-bottom plates l6 of the-troughs l2. The sprays also serve to remove material adhering to and carried over in the rotation of the spiral scrapers 26.

The spiral scrapers 25 have a varying pitch,

the greatest pitch being at the upper end and conditions and to treat the pulp at the desired density.

spiral scrapers may be provided in the upper ends of the troughs. In the drawings, a scraper 25a is shown as mounted in equi-spaced relation to the scraper 25 on each of the shafts 22 and 24 and extending from a point near, but some distance from, the'lower end of each shaft to the upper end. Additional scrapers 25b and 250, mounted in equi-spaced relation to the scrapers 26 and 26a, are shown as extending from a point about one-third of the distance from the lower end of each shaftto be spaced about the shafts 22 and 24 and joined to the scrapers to maintain them in equi-spaced relation. I

While the pitch and number of spiral scrapers used may be varied somewhat to meet different different kinds of materials, 'my investigations have shown that advantageous results may be obtained in treating magnetite ores such as those occurring in the Mesabi district ofjMinnesota if in a concentrator having an inside length of" 18, feet the scraper 25 is mounted on the shaft 22 or the shaft 24 with a pitch of 2 inches between turns for the first 2 feet from the lower end, with a pitch of .4 inches.

section, with a pitch of 8 2-foot section and with a for the, second 2-foot inches forv thethird pitch of lfiinches in In this example, the secondscraper 26a begins at a point 4 feet from the lower end and continues to the upper end with the same variation in pitch as the scraper 25. The scrapers 26b and 26c'begin at a point 6 feet from the lower end and continue to the upper end with a pitch of 16 inches between turns in equi-spacedrela tion to the scrapers 26 and 25a.

1 Figures 6, 7, 8, and 9 show in detail one form of means for adjustment of the relation of the spirals to the pole piece l4. of the apparatus a bracket 48 carries the driving mechanism for the spirals. This bracket 48 is slidably supported on thebracket 52, which is attached rigidly to the sidewalls 20. Threaded members .50 engage the bracket 46 and turn freely in the bracket 52.

By manipulation of the threaded members 59, the bracket 48, carrying the bearings 54 for the spirals, may be raised or lowered vertically with respect tothe pole piece M. The bearings 54 are movable in a, horizontal direction and may be moved toward or away from the pole piece 14 by means of the turnbuckle 55. The pinions 58 are slidably mounted on the shaft 60 so that they may be moved to conform with the horizontal movement of the bearings.

The bearings at the lower end of the apparatus may be adjusted in the same manner as described above for the adjustment of the bearings at the upper end of the apparatus.

Thediagram, Figure 10, shows the preferred adjustment of the spiral. In this diagram, 62 is thevoriginal circumference, 64 is the circumference after wear and 66 is 'the circumference of the spiral when adjusted toits new position. 68 is the original center: and E2 is the new center when the axis of the spiral has been moved along the line 10-10 toward thestrong pole piece l4. If the radius has been reduced by wear one-quarterof an inch, for example, the center should be moved one-quarter of an inch towardthe pole piece 14 along the line lit-iii. Adjustment of the spiral toward the pole piece l4 along the line -|0-'l9 has been found to insure good results in practice. However, it willbe understood that it is not essential that the spiral be adjusted pre-,

the upper end. Beds 29 may the, upper 12-foot sectiom At the upper endiii 933025978 cisely along the line 10-10. The important thing is to adjust it toward orzaway'fro'm the strong pole piece 14. so as to give the'best results with the particular material being treated.

The operation of the apparatus'is as followsr- The comminutediron ore in the form of a-pulp is fed to the apparatus throughthe distributing tendency to sink in the pulp than the unagglom-z erated gangue particles;

As the magnetized particles of iron mineral are.

propelled up the inclined troughs they tend to take a position at or near the pole piece I4; while the heavier gangue particles whichmay also tend to some extent to be propelled up theincline, take a position on the non-magnetic bottom plates l6 of the troughs Ill. The gangueparticles here meet the Water from the spray pipes dfirandare washed down the channels formed by the nonmagnetic bottom plates i6 atthe bottom, of the troughs l2, back into the main body ofthe pulp, where they eventually overflow together with, the lighter gangue particles over the. weir 32. The flow of the gangue 7 particles down the troughs is also facilitated due to the adjustment of the spirals toward the strong pole piece-to compensate for wear and preserve the optimum clearance, which adjustment results in a greater clearance on the sides of the troughs remote from the strong pole piece M. The iron mineral.

collects on the curved surface of thepole piece 14, and is propelled along the sameand finally discharged over the lip-4B through the openings 36.

Owing to the fact that the scrapers:are;.ro-,

tated in such a directionas totend tocarry the magnetic particles of iron mineral up onto the strong pole piece it, the particles collected there on in moving forward tcwardtheconcentrate discharge are carried up out of the liquid pulp,

thereby permitting a large portion ofthe con-p tained water and gangue particles carried there-- by'to drain away and flow back down the troughs 12 toward the tailings discharge. This a marked improvement over my earlier patent above mentioned which contemplated an operation in which the scrapers were-so rotated that the particles'of; iron mineral tended to become remixed with the gangue' particles, thus counteracting the separating efifect of the magnets. I By; arranging the pole pieces in the manner shown androta-te ing the spirals so as to carry the iron mineral 'up out of the bottom of the trough I2, themagnetic mineral being conveyed up the ;inclined trough and the non-magnetic gangue material flowing down the inclined troug-htend to follow separate paths. r 7 V The dewatering and washing of the concentrate is facilitated by providing the elevated discharge lip 49. This lip is made suificiently high to -prevent water introduced through .the spray pipes 46 from flowing out the concentrate discharge opening 36 and carrying therewith any gangue washed away from the concentrate.

As compared with the earlier practicein which concentrate recovered ordinarily contained about 90% watena concentrate mayibe obtained by operating according to the present invention that will contain about 50% water.

V In order closely to control the grade of the concentrate, the spirals are adjusted toward or away from the strong pole piece so as to aiTord optimum results with the" particular material undergoing treatment. desirable to maintain .will vary with the type of material treated over a range of about one-eighth of aninch up to'about one inch.. If the ore isaneasy one to concentrate and contains little middling-theclearance may be smaller; however,

if the Joreis very fine;- containing considerable.

middlingand is .diflicult to separate, the :clear anc'eshould be larger. With one type o-f comparatively coars'eore, i..e.,'65 mesh, very satisev factory, results were obtained when operating with'aclearance of about three-quarters of an inch. Once the optimum clearance has. been d, termined for a particular ore, no further adjustment is .needed except from time to time to compensatefor wear of the spirals. -However,1this feature "of being able to adjust thespirals tocorhpensate for wear is an important one. Heretofore when the spirals had worn so that a clearance of more than about one inch was produced,

itwas necessary tor'replace them with new ones:

By:-me'ans of the adjustable bearingsthelifebf the spiralis greatly prolonged. T

As above statedthe filler pieces 58 are energized. However, it is desirable that the fields so established shall be weakerthan that of the pole piece |.4, in order that the collection of the magi netic ore concentrate on this pole piece shall/be facilitated, While thefiller pieces I8 function as weaker magnetic fields, they may serve'to hasten the .settlingout of the magnetic mineral particles,

which are then transferred to the stronger pole l4,,.dueto rotation of the scrapers.-

While I have shown the pole piece l4 and the filler: pieces l8 as directly in contact with the pulp, it will be understood that the troughs I2 maybe formed separately of a suitable non-mag netic material, withthe pole piece pieces I 8 whenthey are-likewise energized, shaped to conform tothe bottom of the trough, as shown for example in my earlier patent above mentioned. 1 j a V p It will be understood that various other changes may bemade inthe details of construction and operation without departing from the invention' which is not to be deemed. as limited other thanas indicated by the appended claims.

The clearance that it is M and the inclined elongated'agitating zone having a liquid and tailings overflow'at the lower end and a concentrate-discharge at thegllpp r end, magnetic means disposedadjacent said zone to'establish therein a magnetic field varying in intensityfrom one side' of saidzone to the other means; for so agitating a liquid pulp fedto said agitating zone as to move the magneti'zable values contained therein toward the stronger portion of said magnetic field and for conveying them upwardly through said zone to a concentrate.discharge; said-magnetic means being so-disposed with frespect to said agitating zone as to cause the magnetizablevaluesto assume a path in their travel upwardlytoward the concentrate discharge sub.- stantially completely separate from that of the non-magnetic-materials contained in the portions of the liquid pulp that flowdownwardly through said agitating zone toward the liquid. and tailings overflow and said agitating means being adapted to agitate said pulp less 'violently in the lower end of said .zone than: in the: upperend thereof.

2. An ore concentrator comprising an inclined trough having a liquid and tailings overflow at the lower end and a concentrate discharge at the uping located in spaced relation to and above the bottom of said trough, said troughhavin'g a portion adjacent the concentrate discharge extending a substantial distance above the normal water level in the'lower end of said trough as defined by the height of the liquid and tailings overflow, thereby permitting liquids added to and entrained with the concentrate brought into such upper portion to drain away therefrom before such concentrate is discharged from the machine,saidagitating means being adapted to move the magnetizable values in said pulp toward the side of said trough situated in the stronger portion of said magnetic field, and to agitate said pulp less violently in the lower end of said zone than in the upper end thereof, and'means for adjusting said agitating and conveying means toward and away from the bottom of said trough to regulate-the degree of agitation of the'pulp treated in said trough. w 7

3. An ore concentrator comprising an inclined trough curved in cross-sectiom'magnetic. pole pieces extending continuously beneath and along both sides of said trough and conforming-to the curvature thereofimeans for strongly energizing one of said pole pieces and relatively weakly energizing the other pole piece, and a rotating scraper for feeding a material'upwar dly in said trough, said scraper being adapted to be so driven as to tend in rotation to'carry magnetizable values in said material up onto: theside of 'the trough within the magnetic field of said strongpole piece, and being so formed as to maintain a condition of relatively low agitation in the-pulp disposed in the lower end of the trough as compared with the agitation produced thereby inthe upper end thereof.

4. An ore concentrator'comprising an inclined trough, curved in cross-section, and having a liquid overflow at the lower end and a concentrate discharge at'the upper end, a magnetic pole piece extending continuously beneath anda'long one side of said trough andconformingto the curvature thereof, a second magnetic pole piece'dis'- posed adjacent the opposite side of said trough, means for strongly energizing said first-mentioned pole piece and relatively weakly energizing the other pole piece, an agitating and separating conveyorrotatably mounted in said trough and having one en'd'submerged, said conveyor comprising a shaft carrying a continuous spiral scraper varying from a low pitch on the submerged end to a relatively high pitch at the concentrate discharge end of the trough, and means forrotating said conveyor in such direction as to cause it to tend to carry magnetizable values up onto the side of the troughwithin the magnetic field of said first-mentioned pole piece.

5. An ore concentrator comprising an inclined trough, curved in cross-section, and having a liquid overflow at the lower end and a concentrate discharge at the'upper end, a magnetic pole piece conforming to the curvature of the trough and extending beneath and along one side thereof, a second magnetic pole piece disposed adjacent the opposite side of said trough, means for strongly energizing said first-mentioned pole piece and relatively weakly energizing the other pole piece, an agitating and separating conveyor rotatably mounted in said trough and comprising means for producing a relatively small amount of agitation in the lower end of said trough and a relativelyv great amount of agitation in the upper part thereof, said conveyor being so driven asto tend to carry magnetizable values up onto the side of the trough within the magnetic field of said first-mentioned hole piece, means for introducing water into said trough adjacent the concentrate discharge, and means preventing free flow of the water so introduced through the concentrate discharge.

6. An ore concentrator comprising a pair of adjacently arranged inclined troughs, each substantially semi-circular in cross-section, and havinga liquid overflow at the lower end and a con centrate dischargeat the upper end, a magnetic pole piece extending between and beneath said troughs and conforming to the curvature thereof, other pole piecesdisposed adjacent the sides of said troughs remote from said first-mentioned pole piecepmeans for strongly energizing said first-mentioned pole piece and relatively weaklyenergizing the other pole pieces, rotating-scrapers mounted in said troughs for agitating pulp contained therein and conveying solids upwardly in said troughs, and means for so rotating said scrapers as to cause said scrapers to carry magnetic'particles collecting upon said first-mention'ed" pole piece upward upon the same out of the bottom of the troughs and forward toward the concentrate discharge, said scrapers being so formed as to maintain, a condition of relatively low agitation in the pulp disposed in the lower ends of the troughs as compared with the agitation producedthereby in the upper ends thereof. '7; In an ore concentrator comprising an inclined trough, curved in cross-section and having a liquid overflow at the lower end and a concentrate discharge at the upper end, an agitating and separating conveyor rotatably mounted in said trough and having one end submerged, said conveyor comprising a shaft carrying a continuous spiral scraper varying from a low pitch at the submerged end to a relatively high pitch at the concentrate discharge end of the trough, and means for rotating said conveyon 8. In an ore concentrator comprising an inclined trough, curved in cross-section and having a liquid overflow at the lower end and a concentrate discharge at the upper end, an agitating and separating conveyor rotatably mounted in said trough and having one end submerged, said conveyor comprising a shaft carrying a continuous' spiral scraper varying from a low pitch at the submerged end to a relatively high pitch at the concentrate discharge end of the trough, said'shaft also carrying a second spiral scraper beginning at a point near to, but removed from the lower end of the shaft and extending continuously with and in equi-spaced relation to the first-mentioned spiral to the concentrate discharge and of the trough.

9. In an ore concentrator comprising an inclined trough, curved in cross-section, and having a liquid overflow at the lower'end and a concen- 2,002,978 trate discharge at the upper end, an agitating and I separating conveyorrotatably mounted in said trough and having one end submerged, said conveyor comprising a single shaft carrying a continuous spiral scraper, consisting of a portion of low pitch adjacent the lower end, a portion of relatively high pitch adjacent the concentrate disintermediate pitch charge ends, and a portion of between said portions, and a second spiral scraper extending continuously with and in equi-spaced relation to the first-mentioned spiral from a point adjacent the lower end of the intermediate pitched portion of saidfirst-mentioned spiral to a point adjacent the concentrate discharge end.

10. In an ore concentrator comprising an inclined trough, curved in cross-section, and having a liquid overflow at the, lower end and a concentrate discharge at the upper end, an agitating spaced relation to the first-mentioned spiral from a point adjacent the lower end of the intermediate pitched portion of said first-mentioned spiral to a point adjacent the concentrate discharge end, and thirdand fourth spiral scrapers extending continuously with and in equi-spaced relation to the first and second scrapers froma point adjacent the lower end of the high pitched portions of said first and second scrapers to a point'adjacent the concentrate discharge 11. An ore concentrator comprising a trough, curvedin cross-section, and having a liquid overflow at the lower end and a concentrate discharge at the upper end, a magnetic pole piece extending beneath and along one side of said trough, a second magnetic polepiece disposed adjacent the opposite side of said trough, means for strongly energizing said first-mentioned pole piece and relatively weakly energizing the other pole piece, an agitating and separating conveyor rotatably mounted in said trough and having one end submerged, said conveyor comprising a shaft carrying a continuous spiral scraper varying froma low pitch at the submerged end to a relatively high pitch at the concentrate discharge end of the trough, means for rotating said conveyor in such direction as to cause it to tendto carry the concentrate uponto the side of the trough within' the magnetic field of-said first-mentioned pole piece, and means for preventing flow of pulp from the bottom of said trough through the concentrate discharge.

12. An ore concentrator comprising an inclined trough, curved in cross-section, magnetic pole pieces so associated with said trough as to estaband a weaker magnetic field along the other side I lish a strong magnetic field along one side thereof, I

thereof, an agitating and separating conveyor rotatably mounted in said trough and having one end submerged and the other end above the normal pulp' level, means for rotating said conveyor in such direction as to cause it to tend to carry the concentrate up onto the side of the trough within the strongmagnetic field, said conveyor being so formed as to agitate the contents of said trough less violently in the lower portions than in V the upper portions thereof, means for introducing" water into the trough adjacent the upper end thereof, and an elevateddischarge at the upper end of the trough permitting discharge of the,

concentrate as it is fedalong the side of the trough I while preventing flow of liquid pulp through said discharge from the bottom of the trough,

13. An ore concentrator comprising an inclined trough, magnetic poles of unequal strength extending along the bottom and sides of said trough, H

a spiral scraper rotatably mounted in said trough for agitating pulp contained therein and conveying solids upwardly in saidtrough, and'means for adjusting said scraper toward and away from the stronger of said magnetic poles. r

14. An ore concentrator comprising an inclined trough, curved in cross-section, magnetic pole pieces extending continuously beneath and along 'both sides of said trough and conforming to the curvature thereof, means for strongly energizing Y one of said pole pieces and relatively weakly energizing the other pole piece, a rotating scraper;

for feeding a solid material upwardly in said trough, said'scraper being so driven as to carry thematerial up'onto the side'of the trough within the magnetic field of said stron DOle piece, and means for adjusting said scraper toward and away from'said strong pole piece..

. 15. In an ore concentrator comprising'an inclined trough having a liquid overflow at the lower end and. aconcentrate discharge at the 'upper end, an agitating andseparating conveyor rotatably mounted in said trough, magnetic means disposed adjacent said trough for establishing a magnetic field elfective in the space embraced in said trough and varying in intensity from one, side of said trough tothe other, and

means for adjusting said conveyor bodily toward I and away fromthebottom of said troughand toward and away from the side of said trough that is disposed in'the stronger portion of said field, for regulating the degree of agitation of the solids carried by a trough. V

EDWARD WILSON DAVIS.

liquid fed through said 

